The present invention relates to a semiconductor device, an electrical device, and a method of controlling power source of an electrical device.
Recently, there have been widely available such an electrical device provided with a navigation system as a mobile device including a smartphone, a portable navigation system, and the like. Such an electrical device is provided with a GPS (Global Positioning System) device used for the navigation system. In the electrical device, it is necessary to maintain the GPS device in an operation state, so that the GPS device is capable of receiving a GPS signal indicating positional information that is transmitted from a GPS satellite. Accordingly, the GPS device tends to consume a large amount of electrical power, thereby increasing power consumption of a battery thereof. Therefore, in the GPS device, it has been required to reduce power consumption of the battery.
Patent Reference has disclosed a conventional electrical device configured to reduce the power consumption of the power source of the GPS device. The conventional electrical device disclosed in Patent Reference is configured to monitor a reception state of a reception circuit thereof that receives an electrical wave transmitted from the GPS satellite. When the reception circuit is not in the reception state of receiving the electrical wave, the conventional electrical device is configured to shut down power supplied from a power source circuit to the reception circuit. After a specific period of time is elapsed, the conventional electrical device resumes supplying power from the power source circuit to the reception circuit.
Patent Reference: Japanese Patent Publication No. 11-352206
In the conventional electrical device having the GPS device disclosed in Patent Reference, however, it may be sometimes difficult to properly reduce the power consumption thereof. For example, in the conventional electrical device disclosed in Patent Reference, even if the reception state is not ideal for an extended period of time longer than the specific period of time, the conventional electrical device resumes anyway supplying power to the reception circuit to monitor the reception state after the specific period of time is elapsed. Accordingly, in the conventional electrical device disclosed in Patent Reference, power is consumed to monitor the reception state during such an occasion, thereby making it difficult to reduce the power consumption.
In view of the problems described above, an object of the present invention is to provide a semiconductor device and an electrical device having the GPS device capable of solving the problems of the conventional electrical device. A further object of the present invention is to provide a method of controlling a power source. In the present invention, it is possible to reduce the power consumption of the electrical device having the GPS device.
Further objects and advantages of the invention will be apparent from the following description of the invention.